An automatic analyzer discharges a prescribed amount of sample and a prescribed amount of reagent into a reaction cuvette and mixes the sample and the reagent together to cause a reaction. A sample dispensation mechanism of the automatic analyzer is a mechanism for automatically dispensing liquid. For example, the sample dispensation mechanism dispenses a sample, including serum and urine, into a large number of reaction cuvettes in small quantities. The sample dispensation mechanism includes a long and thin probe made of metal or plastic, a tube connected to the probe, and a dispensation syringe arranged at the other end of the tube. The pressure in the tubing is changed by moving a plunger of the dispensation syringe to and fro, by which the sample is suctioned and discharged.
The tubing including the sample probe and the dispensation syringe is usually filled with a liquid (system water), which enables precise suction and discharge of a solution. The diameter of the probe is as small as 0.2 mm to 0.5 mm in order to maintain high dispensation accuracy. Recently, the sample dispensation mechanism is being required to precisely suck in and discharge minute amounts of samples (2 μL or less) and thus the diameter of the sample probe is decreasing further.
High reliability is required of the automatic analyzer as a sample measurement device. The request for high reliability has been met so far by increasing the reliability of the syringe, the dispensation, the channel, or the probe control. Recently, however, not only high reliability but also checking whether the dispensation/discharge operation itself is correctly functioning by use of a pressure sensor or the like is becoming necessary.
It is also being required to issue an alarm after detecting an abnormality in the device control (e.g., clogging of the probe).
For the improvement of reliability, there are two types of technologies: a function of issuing an alarm when an abnormality occurred and a function of checking the amount of a sample/reagent that has been dispensed or sucked in.
As a technology for detection, there is a method of detecting the pressure change in the channel with a pressure sensor and detecting an abnormality by use of the obtained pressure waveform (e.g., in Patent Document 1). This technology is already employed for the detection function of analyzers in order to detect the clogging caused by fibrin, etc. in the samples. In a method for judging whether the clogging has occurred (abnormal state) or not (normal state), the obtained pressure change is recorded and the judgment on abnormality/normality is made on the basis of the distance from normal pressure waveforms by use of the Mahalanobis distance.
While measurement of the dispensation accuracy has been made mainly for samples such as serum and plasma, the objects of the dispensation accuracy measurement are increasing recently, the objects including suction/dispensation of reagents and all samples used.